Re: LR(1) Parsing : Error Handling & Recovery

Stefan Monnier schrieb:
>> IMO a correct PEG parser generator should warn about ambiguities in the
>> grammar, just as every other parser generator does.
>
> AFAIK, there can't be ambiguities in a PEG grammar, because the PEG
> semantics explicitly have a "use the first match" semantics.


How is a grammar related to an specific parser type?


Remember the origin of my comment:
  >>
Take your BNF and pass it to a PEG parser: a PEG parser can accept
pretty much the same input syntax as a BNF parser, and can be considered
as a kind of RD parser, so you'd think the result is necessarily correct.
<<


A grammar primarily describes a language, not an parser. Almost every
parser generator (including PEG) will accept a correct LL(1) grammar,
and the generated parsers will accept the same language. A PEG parser
*also* may be created from a grammar that is rejected by other parser
generators, for contained ambiguities. That's what I consider an
ambiguous grammar.


DoDi

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